Mary Douglas's book, Purity and Danger, is an inquiry into the nature of dirt and cleanliness across different cultures around the world.
The following passage describes how we construct impressions, why it's hard to move away from these impressions, and their seductive potential.
When we encounter something new we try to fit it into our existing categories, “ignoring or distorting” those “uncomfortable facts” that do not find into our pre-established schema so as to not disturb our assumptions.
It seems that whatever we perceive is organized into patterns for which we, the perceivers, are largely responsible. Perceiving is not a matter of passively allowing an organ—say of sight or hearing—to receive a ready-made impression from without, like a palette receiving a spot of paint. Recognizing and remembering are not matters of stirring up old images of past impressions. It is generally agreed that all our impressions are schematically determined from the start. As perceivers we select from all the stimuli falling on our senses only those which interest us, and our interests are governed by a pattern-making tendency, sometimes called a schema. In a chaos of shifting impressions, each of us constructs a stable world in which objects have recognizable shapes, are located in depth, and have permanence. In perceiving we are building, talking some cues and rejecting those which fit most easily into the patter that is being built up. Ambiguous ones tend to be treated as if they harmonized with the rest of the pattern. Discordant ones tend to be rejected. If they are accepted, the structure of assumptions has to be modified. As learning proceeds, objects are named. Their names then affect the way they are perceived next time: Once labelled they are more speedily slotted into the pigeon-holes in future.
As time goes on an experiences pile up, we make a greater and greater investment in our system of labels. So a conservative bias is built in. It gives us confidence. At any time we may have to modify our structure of assumptions to accommodate new experience, but the more consistent experience is with the past, the more confidence we can have in our assumptions.
Uncomfortable facts which refuse to be fitted in, we find ourselves ignoring or distorting so that they do not disturb these established assumptions. By and large anything we take note of is preselected and organized in the very act of perceiving. We share with other animals a kind of filtering mechanism which at first only lets in sensations we know how to use.
Granted that disorder spoils pattern, it also provides the material of pattern. Order implies restriction; from all possible materials, a limited selection has been made and from all possible relations a limited set has been used. So disorder by implication is unlimited, no pattern has been realized in it, but its potential for patterning is indefinite. This is why, though we seek to create order, we do not simply condemn disorder. We recognize that is it destructive to existing patterns; also that it has potentiality. It symbolizes both danger and power.
Sartre writes of the lapidary hardness of the anti-Semite:
How can anyone choose to reason falsely? It is simply the old yearning for impermeability … there are people who are attracted by the permanence of stone. They would like to be solid and impenetrable, they do not want change: for who knows what change might bring? … It is as if their own existence were perpetually in suspense. But they want to exist in all ways at once, and all in once instant … they want to adopt a mode of life in which reasoning and the quest for truth play only a subordinate part, in which nothing is sought expect what has already been found, in which one never becomes anything else by what one already was.
“Powers are attributed to any structure of ideas.” Our inclination is to think that our categories of understanding are real. “This yearning for rigidity is in all of us,” she continues:
It is part of our human condition to long for hard lines and clear concepts. When we have them we have to either face the fact that some realities elude them, or else bind ourselves to the inadequacy of the concepts.